Modeling the effect of size reduction on the stratification of a large wind‐driven lake using an uncertainty‐based approach

Abstract

An important source of uncertainty affecting the results of 3‐D hydrodynamic models of wind‐driven lakes, and one which is rarely formally addressed, arises in the development of spatially and temporally varying wind fields used as surface boundary conditions. We analyze one of the sources of uncertainty in this process and propose a simple and straightforward method to assess the uncertainty in model results arising from the construction of wind fields for surface boundary conditions. Taking into account such uncertainty in model results, it is demonstrated that a 3‐D hydrodynamic model is able to represent mathematically the evolution of the stratification in a large wind‐driven lake. Using the Salton Sea as a case study, and taking model uncertainty into consideration, we demonstrate that a reduction of the lake size, as has been proposed for restoration of the Salton Sea, will induce a stronger and more persistent stratification. These changes in stratification are shown to be statistically significant. As the number of weather stations used to reconstruct the wind field over water increases from three to five, agreement between field and simulated data improves, possibly because of reduced uncertainty in the spatial interpolation of wind data. Differences in stratification between the Salton Sea as it currently exists and as it could exist if restoration plans are implemented, with the lake occupying the northern end of the basin and its surface area reduced by 80%, are the result of the spatial variability of the wind and changes in the magnitude of the wind‐driven mechanical energy fluxes into the lake.